Process for the producing of nitric acid.



F. RAS'CHIG.

PROCESS Fon THE PRODUGTIGN 0F NITRIG ACID.

APPLICATION FILED APR. 21, i914.

Patented Mar. 2,'

on-theRhine, Germany,

of nitric acid; and

FRITZ RASCHIG, 0F LUDWIGSHAFE-ON-THE-RENE, GERMANY.

PROCESS FOB THE FRODUCTIQN OFINITR'IC AGHI?.

. .I P3 specification of Letters Patent.

Patented hier, f5, ilt

Appiicationiled April '21, i914, Serial lo. 533,533.

To all whom it may concern:

Be it known that I, Fnrrz y"tor of philosophy, German Empire, residing' at Ludwigshafenhave invented new Processes for of which the IRAscHio, docand useful. Improvements in the Production -of- Nitric Acid, following isa specification. This invention relates to the production it comprises a continuous process of producin nitric acid from a lnitrate and an acid suc as sodium nitrate and sulfuric acid by distilling such mixture under a high vacuumapproximating aperfl fect vacuum and at a temperature corresponding to such vacuum, the mixture bein run continuously into the distillation vesse and the Iproducts of distillation being continuously removed, While the resulting -b1- sulfate mixture also escapes in a continuous manner; all as more fully hereinafter n v set forth -and as claimed.

It has been heretofore proposed to make nitric acid in a continuous manner from '25.sodium nitrate and sulfuric acid by run- 36'." series of retorts,

overcome ning the mixture through awetort or series of retorts maintained at ordinary at mospheric pressure and at a progressively increasing temperature; in the case of a the temperature being that necessary to edect the reaction and distillation at this pressure. -But this process has the disadvantage resulting from the necessar I. high temperatures, of about v270" C., the wear and tear of .the apparatus caused by this heat: lt has also-heen. proposed to make'nitric acid of high degree of purity by carrying out the reaction n vacuo, but this process, While giving high 40' strength' acid and goed yields, is intermittent and requires discharging and recharging of the apparatus after the distillation of leach charge.

it is an object of the present invention Vto these disadvantages, and to produce nitric acid from nitrate and sulfuric acid, or their equivalents by a process which is not only a vacuum process using a high chemist,a citizen ofv` the y Pump vhaving a suitable inlet b and outlet o.

The process of the present invention oomprises the continuous distillation of a' mix 4ture of'sodiurn nitrate und 'sulfuric acid,

'or their equivalents, by allowing a duid or pasty mixture of the sodium nitrate and sulfuric acid to run continuiousltv into one vend of a heated voeu in pan. tu this pan they nitric acid is generated und o'istilled ed at a temperature of efi'to 1705 C. into a itable condenser; From this pan the ilquid bisulfate remaining aiiter'the distiilation, escapeswat the other and remote end, the inlet and outlet connections, as Well as the condenser outlet, being pipes atleast six ymeters long. rIlle vacuum in the vacuum pan is maintained by a suitablel vacuum attached to the condenser,I or by other suitabic means, so -that a vacuum is main tained. corresponding to the head ci liquid in saidbarorneter pipes of six meters length, it being understood that the head of liquid in these pipes will depend somewhat on the specific gravity "of the liquid mixture, as Well as upon the barometric pressure.

In the accompanying drawings is illustrated one form ci" apparatus in which the process of the present invention can be practised. It is understood that the. invention is illustrated by, but not coniined to, this particular form or construction of apparatus.

'in these drawings Figure l shows the ap paratus as a Whole u'vith partslshoufn in section, matic; and Fig. 2 is .a top View of 'the vacuum pan with the cover` removed, this illustration heiug also diagrammatic.

The apparatus illustrated comprises a fiat cast iron pan c separated hy' partitions estending alternately from each side to near the. other side to form a prolonged zigzag course for the li uid passing through it, and rl`he be heated in any suitvacuum pan c may the illustration being in part diagramv able manner, as by direct Ilame or steam, but '100 is shown as having a steam coil embedded in its .bottom wall, steam being supplied at a temperature e. y. about '1700 C. and a cor-- responding pressure of about twelve or ourvacuum, out which is also a continuous W process carried out under a'hgh vacuum teen atmospheres. Frorn the top of the we and at a correspondingly lower .tempera- 'fvacuum pan the nitric' acid vapors are conture which new process avoids the Wear and ducted through a vcondensing coil d made tear and corroding action caused by the high of a pipe of clay or of other suitable matetemperatures necessary et ordinary presrial. The vapors are here condensed and 6 5 sure. flow into the aluminum tube e attached to lio theacenuenser and having a length of about seven meters, the lower end of thispipe being' immersed in a suitable receptacle f for receiving the nitric acid. This receptacle is also of aluminum and has asuitable outlet g. The pipe k, also attached to the coil, connects with the wet pump which is fed with milk of lime toneutralize and render innocuous any acid fumes entering-the pump. The inlet b'has attached thereto a suitable pipe K which is at least six meters long` and reaches into a lvessel l at its lower end. The outlet c is also connected to asimilar pipe m, which .may be of iron, through which the'liquid bisulfateruns intothe receptacle n' prvided with suitable overliow or outlet .of

-In'order to prevent cooling and solidify:

ing of the bisulate inthe pipe m,.feither during the operation of the a paratus, or

' when the apparatus is out of or er, this 'pipe is provided with' suitable 'heating means,

shown as .a steam pipe p-g extending.

through an extension of the pipe m, and bringing the steam into heat interchanging relation therewith. In 'orderto prevent solidifying of the bisulfat'e inthe receptacle n, if the apparatus should become out of order, this' receptacle is .provided with a lower discharge 'r to permit emptying.,

In the operation of this apparatus, and the practising of the process of the present invention, the mixture of sodium nitrate and sulfuric acid, or their equivalents, is placed in the receptacle Z. This mixture may be 'made up, for example, of 100 parts.' of

' sodium nitrate (96% and 130 parts of sul,-

furic acid (94%).' n starting the apparatus'thev receptacle ln. is filled with concentrated sulfuric acid,'f with nitric acid, andil Awith the mixture indicated. The pan a 1s then heated by the steam coil, and also the pipe m by the steam pipe p-g, and the vacuum pump is put, in operation. At the same time an even current of the above mixture is run into the receptacle Z. Itwill be noted that this receptacle' extends above the receptacles n .and f and that its liquid contents also can extend abovethe liquid level of these other receptacles. As the vacuum pump sucks the air andy gases out of the apparatus the atmospheric pressure'forces the liquids from these' various' receptacles into the barometer pipes e, 7c and m, the height of I liquid beingdetermined by the dillereice between th'epres'sure in the apparatus and the atmospheric pressure. 'The length of the pipes e and m, however, are usually such that the liquid cannot be drawn back into the apparatus. The' length 'of these pipes is greater than the height of the f columns of liquid correspondi ton a perfeet vacuum, while the lengthnfD the inlet pipe K and the height ofthe level q .f liquid in its receptacle Zare such that thfe' liquid column is less .than-'that' corresponding tov dicated, and in'this pan, owing to the in uence of, theheat, the nitricacid is evolved and removed, escaping through thev condenser d into the pipe 'ep-and the-receptacle f, from nthichit. esca es at g.- Thebisulfate formed and resultlng from thedistillation, escapes .at c into the pipe m and thence into the receptaclen, replacing thesulfuric acid originally laced in this receptacle until finally thelb suitable molds orrecepta'cles in which it isulfateg'escapes at o into may` be permitted-to cool' and solidify.l It

- will be understood that the'head of. liquid in the pipes mand e corresponds to thedegreeo .vacuum 1n the vacuum pan, or, in

other Words, tothe difference ,in pressure be` tween that inthe pan andftiieatmos heric pressure, whilepthe'head ofT-liquid 1n .the pipe K isslightly less than thatcorrespondmg to this difference, so that the outside atmospheric pressure forcesthe liquid ,-mixture up through this pipe into the apparatus, vthis liquid being replenished in the re-Vv ceptacle Zjin a continuous manner, and the" rate ofviow being thus controlled. The zigzag arrangement of the vacuum pan causes the liquid in it to `travel in a prolonged .course and tobe exposedcontinuously to the heating action so that completion of the,

process 1s insured.

` It will be seen that the process ofthe pres- 'ent' invention is continuous in operation, that 1t operates at a hlgh Vacuum approximating' a perfect vacuum, that a much lower temperature can be utilized, and',1 that no 'other operating mechanism than the;y vacuum pump 1s necessary-"The 4temperature used, about 170. C., is about v100 lower atha'nthat necessary in processes carriedl out at atmospheric pressure, vWhere aftemperatulre of around 270 C. must be applied. The use' of a low temperature causes a corresponding economy in fuel, and a material saving in the Wear and tear ofthe apparatus, due to corrosion, etc. The present process, moreover, gives an excellent yield of high percentage nitric acid.

It will be understood that 'variations and modifications may be madein the processofl the i present. invention 'Withoutv departing' therefrom ;l and that'other specicstructures of apparatus may also be employed in carrying out this process; it being intended to illustrate the invention by the specific ein izo lac

medion hodiment thereof described in this specification, but not to limit the invention to the same.

I claim:

1. The continuous process of producing nitric acid from a mixture of a nitrate and sulfuric a`cid, which comprises distilling such mixture under a high vacuum, continu- ,ously removing the nitric acid evolved, supplying such mixture in a continuous manto be distilled, and also removing the. bisulfate formed in a continuous manner.

2. The continuous process of producing nitric acid from a mixture of sodium nitrate and sulfuric acid, which comprises distilling such mixture at a temperature of about 170 and under a high vacuum corresponding to this temperature, continuously removing the nitrlcacid evolved, supplying such mixture in a continuous manner to be distilled, and also remoying the hisulfate formed in a continuous manner.

3. The continuous process of producing nitric acid from a mixture of anitrate and sulfuric acid, which comprises distilling such mixture under a high vacuum approximating a perfect vacuum, continuously removing the nitric acid evolved, supplying such mixture at a 'temperature of about 170 and under a high vacuum corresponding to `this temperature, continuously removing the nitric acid evolved, supplying such mixture in a continuous manner through a conduit containing therein a head of liquid correspending approximately to the vacuum employed, and also removing the bisuifate formed in a continuous manner through a.

conduit containing a head of liquid corresponding to the vacuum employed.

En testimony whereof have hereunto set my hand in the presence of two subscribing witnesses.

FRITZ RASCHG. Witnesses:

ROBERT GERLACH, RICHARD Rumen-:Ln 

